As the first military shooter on PS Vita, Unit 13 has the market more or less to itself, but it's a game that comes some way short of delivering on its portable gaming promise.

Tying together the missions is a leaderboard system that shows you how you're doing in each challenge compared to friends, people locally (via Near) or globally. This is all well and good, but I never felt compelled to strive for high scores. Compared to the other Vita title currently offering a lot in terms of social integration, MotorStorm RC, Unit 13 simply doesn't make a big enough deal out of its leaderboards. They are there, but the game doesn't make you care about them.

Each mission can be tackled cooperatively with a friend, which in many instances does improve the level of enjoyment you'll get from the game by virtue of making things a lot easier - and voice chat works surprisingly well. It doesn't make what you do any more exciting, though, with the basic list of mission objectives becoming rather samey way before the final mission.

Extra challenges are offered through the High Value Targets missions, unlocked after earning a certain number of gold stars through the main 36 levels. While these play out in much the same way as before, the overall goal is to assassinate a certain NPC and getting there means killing an awful lot of grunts.

There are also daily challenges, which is the one thing the game seems to make a big deal out of in terms of the social networking. The idea of a new daily event is a good one, and its time-limited nature and one-shot mentality instantly makes it more appealing to take part in, but the general re-use of maps will surely make this less appealing in the weeks to come.

Visuals might not mean as much to Unit 13's overall goal than its social features, but it's still a shame that the game doesn't look a bit more impressive. Occasionally your decently modelled character will be stood in a room with the light hitting in just the right way, his shadow being cast across the ground, that you'll think, "actually, this isn't a bad looking game," but then you'll head outside and find a drab level populated so sparsely that the whole thing feels unfinished - which is more or less a statement about the game as a whole.

As the first military shooter on PS Vita, Unit 13 has the market more or less to itself, but it's a game that comes some way short of delivering on its portable gaming promise. Certain key aspects of the game don't feel like they've had enough time spent on them, so the result is a game that is on the right tracks but more of a taster of things to come than something Vita owners should celebrate.